Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[Hannes Reinecke]

On 09/17/2015 07:33 AM, Michael S. Tsirkin wrote:
> On Wed, Sep 16, 2015 at 07:29:17PM -0500, Suman Anna wrote:
>> The virtio core uses a static ida named virtio_index_ida for
>> assigning index numbers to virtio devices during registration.
>> The ida core may allocate some internal idr cache layers and
>> an ida bitmap upon any ida allocation, and all these layers are
>> truely freed only upon the ida destruction. The virtio_index_ida
>> is not destroyed at present, leading to a memory leak when using
>> the virtio core as a module and atleast one virtio device is
>> registered and unregistered.
>>
>> Fix this by invoking ida_destroy() in the virtio core module
>> exit.
>>
>> Cc: "Michael S. Tsirkin" 
>> Signed-off-by: Suman Anna 
> 
> Interesting.
> Will the same apply to e.g. sd_index_ida in drivers/scsi/sd.c
> or iscsi_sess_ida in drivers/scsi/scsi_transport_iscsi.c?
> 
> If no, why not?
> 
> One doesn't generally expect to have to free global variables.
> Maybe we should forbid DEFINE_IDA in modules?
> 
> James, could you comment on this please?
> 
Well, looking at the code 'ida_destroy' only need to be called
if you want/need to do a general cleanup.
It shouldn't be required if you do correct reference counting
on your objects, and call idr_remove() on each of them.

Unless I'm misreading something.

Seems like a topic for KS; Johannes had a larger patchset recently to
clean up idr, which run into very much the same issues.

Cheers,

Hannes

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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[James Bottomley]

On Thu, 2015-09-17 at 08:33 +0300, Michael S. Tsirkin wrote:
> On Wed, Sep 16, 2015 at 07:29:17PM -0500, Suman Anna wrote:
> > The virtio core uses a static ida named virtio_index_ida for
> > assigning index numbers to virtio devices during registration.
> > The ida core may allocate some internal idr cache layers and
> > an ida bitmap upon any ida allocation, and all these layers are
> > truely freed only upon the ida destruction. The virtio_index_ida
> > is not destroyed at present, leading to a memory leak when using
> > the virtio core as a module and atleast one virtio device is
> > registered and unregistered.
> > 
> > Fix this by invoking ida_destroy() in the virtio core module
> > exit.
> > 
> > Cc: "Michael S. Tsirkin" 
> > Signed-off-by: Suman Anna 
> 
> Interesting.
> Will the same apply to e.g. sd_index_ida in drivers/scsi/sd.c
> or iscsi_sess_ida in drivers/scsi/scsi_transport_iscsi.c?
> 
> If no, why not?
> 
> One doesn't generally expect to have to free global variables.
> Maybe we should forbid DEFINE_IDA in modules?
> 
> James, could you comment on this please?

ida is Tejun's baby (cc'd).  However, it does look like without
ida_destroy() you will leave a cached ida->bitmap dangling because we're
trying to be a bit clever in ida_remove() so we cache the bitmap to
relieve ida_pre_get() of the burden if we would otherwise free it.

I don't understand why you'd want to forbid DEFINE_IDA ... all it does
is pre-initialise a usually static ida structure.  The initialised
structure will have a NULL bitmap cache that's allocated in the first
ida_pre_get() ... that all seems to work as expected and no different
from a dynamically allocated struct ida.  Or are you thinking because
ida_destory() doesn't set bitmap to NULL, it damages the reuse?  In
which case I'm not sure there's much benefit to making it reusable, but
I suppose we could by adding a memset into ida_destroy().

James

> > ---
> >  drivers/virtio/virtio.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> > index b1877d73fa56..7062bb0975a5 100644
> > --- a/drivers/virtio/virtio.c
> > +++ b/drivers/virtio/virtio.c
> > @@ -412,6 +412,7 @@ static int virtio_init(void)
> >  static void __exit virtio_exit(void)
> >  {
> > bus_unregister(_bus);
> > +   ida_destroy(_index_ida);
> >  }
> >  core_initcall(virtio_init);
> >  module_exit(virtio_exit);
> > -- 
> > 2.5.0
> --
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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[James Bottomley]

On Thu, 2015-09-17 at 19:06 +0300, Michael S. Tsirkin wrote:
> On Thu, Sep 17, 2015 at 07:15:44AM -0700, James Bottomley wrote:
> > On Thu, 2015-09-17 at 08:33 +0300, Michael S. Tsirkin wrote:
> > > On Wed, Sep 16, 2015 at 07:29:17PM -0500, Suman Anna wrote:
> > > > The virtio core uses a static ida named virtio_index_ida for
> > > > assigning index numbers to virtio devices during registration.
> > > > The ida core may allocate some internal idr cache layers and
> > > > an ida bitmap upon any ida allocation, and all these layers are
> > > > truely freed only upon the ida destruction. The virtio_index_ida
> > > > is not destroyed at present, leading to a memory leak when using
> > > > the virtio core as a module and atleast one virtio device is
> > > > registered and unregistered.
> > > > 
> > > > Fix this by invoking ida_destroy() in the virtio core module
> > > > exit.
> > > > 
> > > > Cc: "Michael S. Tsirkin" 
> > > > Signed-off-by: Suman Anna 
> > > 
> > > Interesting.
> > > Will the same apply to e.g. sd_index_ida in drivers/scsi/sd.c
> > > or iscsi_sess_ida in drivers/scsi/scsi_transport_iscsi.c?
> > > 
> > > If no, why not?
> > > 
> > > One doesn't generally expect to have to free global variables.
> > > Maybe we should forbid DEFINE_IDA in modules?
> > > 
> > > James, could you comment on this please?
> > 
> > ida is Tejun's baby (cc'd).  However, it does look like without
> > ida_destroy() you will leave a cached ida->bitmap dangling because we're
> > trying to be a bit clever in ida_remove() so we cache the bitmap to
> > relieve ida_pre_get() of the burden if we would otherwise free it.
> > 
> > I don't understand why you'd want to forbid DEFINE_IDA ... all it does
> > is pre-initialise a usually static ida structure.  The initialised
> > structure will have a NULL bitmap cache that's allocated in the first
> > ida_pre_get() ... that all seems to work as expected and no different
> > from a dynamically allocated struct ida.  Or are you thinking because
> > ida_destory() doesn't set bitmap to NULL, it damages the reuse?  In
> > which case I'm not sure there's much benefit to making it reusable, but
> > I suppose we could by adding a memset into ida_destroy().
> > 
> > James
> 
> It's just unusual to have  a descructor without a constructor.
> I bet more drivers misuse this AI because of this.


Well, there's an easy fix for that.  We could have ida_remove() actually
free the bitmap and not cache it if it's the last layer.  That way ida
would naturally empty and we wouldn't need a destructor.   Tejun, would
that work?

James

> > > > ---
> > > >  drivers/virtio/virtio.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> > > > index b1877d73fa56..7062bb0975a5 100644
> > > > --- a/drivers/virtio/virtio.c
> > > > +++ b/drivers/virtio/virtio.c
> > > > @@ -412,6 +412,7 @@ static int virtio_init(void)
> > > >  static void __exit virtio_exit(void)
> > > >  {
> > > > bus_unregister(_bus);
> > > > +   ida_destroy(_index_ida);
> > > >  }
> > > >  core_initcall(virtio_init);
> > > >  module_exit(virtio_exit);
> > > > -- 
> > > > 2.5.0
> > > --
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> > > the body of a message to majord...@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > 
> > 
> > 
> > 
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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[James Bottomley]

On Thu, 2015-09-17 at 13:15 -0400, Tejun Heo wrote:
> Hello,
> 
> On Thu, Sep 17, 2015 at 09:48:37AM -0700, James Bottomley wrote:
> > Well, there's an easy fix for that.  We could have ida_remove() actually
> > free the bitmap and not cache it if it's the last layer.  That way ida
> > would naturally empty and we wouldn't need a destructor.   Tejun, would
> > that work?
> 
> Yeah, that definitely is one way to go about it.  It kinda muddles the
> purpose of ida_destroy() tho.  I suppose we can rename it to
> idr_remove_all() and then do the same to idr.  I'm not particularly
> objecting to all that but what's wrong with just calling idr_destroy()
> on exit paths?  If missing the call in modules is an issue, maybe we
> can just annotate idr/ida with debugobj?

The argument is that we shouldn't have to explicitly destroy a
statically initialized object, so 

DEFINE_IDA(someida);

Should just work without having to explicitly do

ida_destory(someida);

somewhere in the exit code.  It's about usage patterns.  Michael's
argument is that if we can't follow the no destructor pattern for
DEFINE_IDA() then we shouldn't have it at all, because it's confusing
kernel design patterns.  The pattern we would have would be

struct ida someida:

ida_init();

...

ida_destroy();

so the object explicitly has a constructor matched to a destructor.

James


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[PATCH] iscsi: make mutex for target scanning and unbinding per-session

[Chris Leech]

Currently the iSCSI transport class synchronises target scanning and
unbinding with a host level mutex.  For multi-session hosts (offloading
iSCSI HBAs) connecting to storage arrays that may implement one
target-per-lun, this can result in the target scan work for hundreds of
sessions being serialized behind a single mutex.  With slow enough
response times, this can cause scan requests initiated from userspace to
block on the mutex long enough to trigger 120 sec hung task warnings.

I can't see any reason not to move this to a session level mutex and let
the target scans run in parallel, speeding up connecting to a large
number of targets.  Note that as iscsi_tcp creates a virtual host for
each session, software iSCSI is effectively doing this already.

Signed-off-by: Chris Leech 
---
 drivers/scsi/scsi_transport_iscsi.c | 19 ++-
 include/scsi/scsi_transport_iscsi.h |  2 +-
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/scsi_transport_iscsi.c 
b/drivers/scsi/scsi_transport_iscsi.c
index e4b3d8f..9daeb7f 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -1569,7 +1569,6 @@ static int iscsi_setup_host(struct transport_container 
*tc, struct device *dev,
 
memset(ihost, 0, sizeof(*ihost));
atomic_set(>nr_scans, 0);
-   mutex_init(>mutex);
 
iscsi_bsg_host_add(shost, ihost);
/* ignore any bsg add error - we just can't do sgio */
@@ -1789,8 +1788,6 @@ static int iscsi_user_scan_session(struct device *dev, 
void *data)
 {
struct iscsi_scan_data *scan_data = data;
struct iscsi_cls_session *session;
-   struct Scsi_Host *shost;
-   struct iscsi_cls_host *ihost;
unsigned long flags;
unsigned int id;
 
@@ -1801,10 +1798,7 @@ static int iscsi_user_scan_session(struct device *dev, 
void *data)
 
ISCSI_DBG_TRANS_SESSION(session, "Scanning session\n");
 
-   shost = iscsi_session_to_shost(session);
-   ihost = shost->shost_data;
-
-   mutex_lock(>mutex);
+   mutex_lock(>mutex);
spin_lock_irqsave(>lock, flags);
if (session->state != ISCSI_SESSION_LOGGED_IN) {
spin_unlock_irqrestore(>lock, flags);
@@ -1823,7 +1817,7 @@ static int iscsi_user_scan_session(struct device *dev, 
void *data)
}
 
 user_scan_exit:
-   mutex_unlock(>mutex);
+   mutex_unlock(>mutex);
ISCSI_DBG_TRANS_SESSION(session, "Completed session scan\n");
return 0;
 }
@@ -1999,26 +1993,24 @@ static void __iscsi_unbind_session(struct work_struct 
*work)
struct iscsi_cls_session *session =
container_of(work, struct iscsi_cls_session,
 unbind_work);
-   struct Scsi_Host *shost = iscsi_session_to_shost(session);
-   struct iscsi_cls_host *ihost = shost->shost_data;
unsigned long flags;
unsigned int target_id;
 
ISCSI_DBG_TRANS_SESSION(session, "Unbinding session\n");
 
/* Prevent new scans and make sure scanning is not in progress */
-   mutex_lock(>mutex);
+   mutex_lock(>mutex);
spin_lock_irqsave(>lock, flags);
if (session->target_id == ISCSI_MAX_TARGET) {
spin_unlock_irqrestore(>lock, flags);
-   mutex_unlock(>mutex);
+   mutex_unlock(>mutex);
return;
}
 
target_id = session->target_id;
session->target_id = ISCSI_MAX_TARGET;
spin_unlock_irqrestore(>lock, flags);
-   mutex_unlock(>mutex);
+   mutex_unlock(>mutex);
 
if (session->ida_used)
ida_simple_remove(_sess_ida, target_id);
@@ -2051,6 +2043,7 @@ iscsi_alloc_session(struct Scsi_Host *shost, struct 
iscsi_transport *transport,
INIT_WORK(>unbind_work, __iscsi_unbind_session);
INIT_WORK(>scan_work, iscsi_scan_session);
spin_lock_init(>lock);
+   mutex_init(>mutex);
 
/* this is released in the dev's release function */
scsi_host_get(shost);
diff --git a/include/scsi/scsi_transport_iscsi.h 
b/include/scsi/scsi_transport_iscsi.h
index 6183d20..acf9d9d 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -238,6 +238,7 @@ struct iscsi_cls_session {
struct work_struct unblock_work;
struct work_struct scan_work;
struct work_struct unbind_work;
+   struct mutex mutex;
 
/* recovery fields */
int recovery_tmo;
@@ -272,7 +273,6 @@ struct iscsi_cls_session {
 
 struct iscsi_cls_host {
atomic_t nr_scans;
-   struct mutex mutex;
struct request_queue *bsg_q;
uint32_t port_speed;
uint32_t port_state;
-- 
2.1.0

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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[Tejun Heo]

Hello,

On Thu, Sep 17, 2015 at 09:48:37AM -0700, James Bottomley wrote:
> Well, there's an easy fix for that.  We could have ida_remove() actually
> free the bitmap and not cache it if it's the last layer.  That way ida
> would naturally empty and we wouldn't need a destructor.   Tejun, would
> that work?

Yeah, that definitely is one way to go about it.  It kinda muddles the
purpose of ida_destroy() tho.  I suppose we can rename it to
idr_remove_all() and then do the same to idr.  I'm not particularly
objecting to all that but what's wrong with just calling idr_destroy()
on exit paths?  If missing the call in modules is an issue, maybe we
can just annotate idr/ida with debugobj?

Thanks.

-- 
tejun

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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[Tejun Heo]

Hello, James.

On Thu, Sep 17, 2015 at 10:58:29AM -0700, James Bottomley wrote:
> The argument is that we shouldn't have to explicitly destroy a
> statically initialized object, so 
> 
> DEFINE_IDA(someida);
> 
> Should just work without having to explicitly do
> 
> ida_destory(someida);
> 
> somewhere in the exit code.  It's about usage patterns.  Michael's
> argument is that if we can't follow the no destructor pattern for
> DEFINE_IDA() then we shouldn't have it at all, because it's confusing
> kernel design patterns.  The pattern we would have would be
> 
> struct ida someida:
> 
> ida_init();
> 
> ...
> 
> ida_destroy();
> 
> so the object explicitly has a constructor matched to a destructor.

Yeah, I get that.  I'm just not convinced that this matters enough
especially if we can get debugobj/ksan/whatever trip on it.

Thanks.

-- 
tejun

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DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[Michael S. Tsirkin]

On Wed, Sep 16, 2015 at 07:29:17PM -0500, Suman Anna wrote:
> The virtio core uses a static ida named virtio_index_ida for
> assigning index numbers to virtio devices during registration.
> The ida core may allocate some internal idr cache layers and
> an ida bitmap upon any ida allocation, and all these layers are
> truely freed only upon the ida destruction. The virtio_index_ida
> is not destroyed at present, leading to a memory leak when using
> the virtio core as a module and atleast one virtio device is
> registered and unregistered.
> 
> Fix this by invoking ida_destroy() in the virtio core module
> exit.
> 
> Cc: "Michael S. Tsirkin" 
> Signed-off-by: Suman Anna 

Interesting.
Will the same apply to e.g. sd_index_ida in drivers/scsi/sd.c
or iscsi_sess_ida in drivers/scsi/scsi_transport_iscsi.c?

If no, why not?

One doesn't generally expect to have to free global variables.
Maybe we should forbid DEFINE_IDA in modules?

James, could you comment on this please?

> ---
>  drivers/virtio/virtio.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index b1877d73fa56..7062bb0975a5 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -412,6 +412,7 @@ static int virtio_init(void)
>  static void __exit virtio_exit(void)
>  {
>   bus_unregister(_bus);
> + ida_destroy(_index_ida);
>  }
>  core_initcall(virtio_init);
>  module_exit(virtio_exit);
> -- 
> 2.5.0

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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[Michael S. Tsirkin]

On Thu, Sep 17, 2015 at 07:15:44AM -0700, James Bottomley wrote:
> On Thu, 2015-09-17 at 08:33 +0300, Michael S. Tsirkin wrote:
> > On Wed, Sep 16, 2015 at 07:29:17PM -0500, Suman Anna wrote:
> > > The virtio core uses a static ida named virtio_index_ida for
> > > assigning index numbers to virtio devices during registration.
> > > The ida core may allocate some internal idr cache layers and
> > > an ida bitmap upon any ida allocation, and all these layers are
> > > truely freed only upon the ida destruction. The virtio_index_ida
> > > is not destroyed at present, leading to a memory leak when using
> > > the virtio core as a module and atleast one virtio device is
> > > registered and unregistered.
> > > 
> > > Fix this by invoking ida_destroy() in the virtio core module
> > > exit.
> > > 
> > > Cc: "Michael S. Tsirkin" 
> > > Signed-off-by: Suman Anna 
> > 
> > Interesting.
> > Will the same apply to e.g. sd_index_ida in drivers/scsi/sd.c
> > or iscsi_sess_ida in drivers/scsi/scsi_transport_iscsi.c?
> > 
> > If no, why not?
> > 
> > One doesn't generally expect to have to free global variables.
> > Maybe we should forbid DEFINE_IDA in modules?
> > 
> > James, could you comment on this please?
> 
> ida is Tejun's baby (cc'd).  However, it does look like without
> ida_destroy() you will leave a cached ida->bitmap dangling because we're
> trying to be a bit clever in ida_remove() so we cache the bitmap to
> relieve ida_pre_get() of the burden if we would otherwise free it.
> 
> I don't understand why you'd want to forbid DEFINE_IDA ... all it does
> is pre-initialise a usually static ida structure.  The initialised
> structure will have a NULL bitmap cache that's allocated in the first
> ida_pre_get() ... that all seems to work as expected and no different
> from a dynamically allocated struct ida.  Or are you thinking because
> ida_destory() doesn't set bitmap to NULL, it damages the reuse?  In
> which case I'm not sure there's much benefit to making it reusable, but
> I suppose we could by adding a memset into ida_destroy().
> 
> James

It's just unusual to have  a descructor without a constructor.
I bet more drivers misuse this AI because of this.

> > > ---
> > >  drivers/virtio/virtio.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> > > index b1877d73fa56..7062bb0975a5 100644
> > > --- a/drivers/virtio/virtio.c
> > > +++ b/drivers/virtio/virtio.c
> > > @@ -412,6 +412,7 @@ static int virtio_init(void)
> > >  static void __exit virtio_exit(void)
> > >  {
> > >   bus_unregister(_bus);
> > > + ida_destroy(_index_ida);
> > >  }
> > >  core_initcall(virtio_init);
> > >  module_exit(virtio_exit);
> > > -- 
> > > 2.5.0
> > --
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Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

[Tejun Heo]

Hello,

On Thu, Sep 17, 2015 at 07:15:44AM -0700, James Bottomley wrote:
> I don't understand why you'd want to forbid DEFINE_IDA ... all it does

I guess to require the use of explicit init / creation so that it's
clear the data structure needs to be destroyed?

> is pre-initialise a usually static ida structure.  The initialised
> structure will have a NULL bitmap cache that's allocated in the first
> ida_pre_get() ... that all seems to work as expected and no different
> from a dynamically allocated struct ida.  Or are you thinking because
> ida_destory() doesn't set bitmap to NULL, it damages the reuse?  In
> which case I'm not sure there's much benefit to making it reusable, but
> I suppose we could by adding a memset into ida_destroy().

I don't know.  Data structures which do lazy anything would likely
need explicit destruction and I'm not sure we'd wanna ban static
initialization for all such cases.  Seems like an unnecessary
restriction.

Thanks.

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Re: [PATCH] iscsi: make mutex for target scanning and unbinding per-session

[Mike Christie]

On 9/17/15, 1:16 PM, Chris Leech wrote:

Currently the iSCSI transport class synchronises target scanning and
unbinding with a host level mutex.  For multi-session hosts (offloading
iSCSI HBAs) connecting to storage arrays that may implement one
target-per-lun, this can result in the target scan work for hundreds of
sessions being serialized behind a single mutex.  With slow enough
response times, this can cause scan requests initiated from userspace to
block on the mutex long enough to trigger 120 sec hung task warnings.

I can't see any reason not to move this to a session level mutex and let
the target scans run in parallel, speeding up connecting to a large
number of targets.  Note that as iscsi_tcp creates a virtual host for
each session, software iSCSI is effectively doing this already.

Signed-off-by: Chris Leech 
---
  drivers/scsi/scsi_transport_iscsi.c | 19 ++-
  include/scsi/scsi_transport_iscsi.h |  2 +-
  2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/scsi_transport_iscsi.c 
b/drivers/scsi/scsi_transport_iscsi.c
index e4b3d8f..9daeb7f 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -1569,7 +1569,6 @@ static int iscsi_setup_host(struct transport_container 
*tc, struct device *dev,

memset(ihost, 0, sizeof(*ihost));
atomic_set(>nr_scans, 0);
-   mutex_init(>mutex);

iscsi_bsg_host_add(shost, ihost);
/* ignore any bsg add error - we just can't do sgio */
@@ -1789,8 +1788,6 @@ static int iscsi_user_scan_session(struct device *dev, 
void *data)
  {
struct iscsi_scan_data *scan_data = data;
struct iscsi_cls_session *session;
-   struct Scsi_Host *shost;
-   struct iscsi_cls_host *ihost;
unsigned long flags;
unsigned int id;

@@ -1801,10 +1798,7 @@ static int iscsi_user_scan_session(struct device *dev, 
void *data)

ISCSI_DBG_TRANS_SESSION(session, "Scanning session\n");

-   shost = iscsi_session_to_shost(session);
-   ihost = shost->shost_data;
-
-   mutex_lock(>mutex);
+   mutex_lock(>mutex);
spin_lock_irqsave(>lock, flags);
if (session->state != ISCSI_SESSION_LOGGED_IN) {
spin_unlock_irqrestore(>lock, flags);
@@ -1823,7 +1817,7 @@ static int iscsi_user_scan_session(struct device *dev, 
void *data)
}

  user_scan_exit:
-   mutex_unlock(>mutex);
+   mutex_unlock(>mutex);
ISCSI_DBG_TRANS_SESSION(session, "Completed session scan\n");
return 0;
  }
@@ -1999,26 +1993,24 @@ static void __iscsi_unbind_session(struct work_struct 
*work)
struct iscsi_cls_session *session =
container_of(work, struct iscsi_cls_session,
 unbind_work);
-   struct Scsi_Host *shost = iscsi_session_to_shost(session);
-   struct iscsi_cls_host *ihost = shost->shost_data;
unsigned long flags;
unsigned int target_id;

ISCSI_DBG_TRANS_SESSION(session, "Unbinding session\n");

/* Prevent new scans and make sure scanning is not in progress */
-   mutex_lock(>mutex);
+   mutex_lock(>mutex);
spin_lock_irqsave(>lock, flags);
if (session->target_id == ISCSI_MAX_TARGET) {
spin_unlock_irqrestore(>lock, flags);
-   mutex_unlock(>mutex);
+   mutex_unlock(>mutex);
return;
}

target_id = session->target_id;
session->target_id = ISCSI_MAX_TARGET;
spin_unlock_irqrestore(>lock, flags);
-   mutex_unlock(>mutex);
+   mutex_unlock(>mutex);

if (session->ida_used)
ida_simple_remove(_sess_ida, target_id);
@@ -2051,6 +2043,7 @@ iscsi_alloc_session(struct Scsi_Host *shost, struct 
iscsi_transport *transport,
INIT_WORK(>unbind_work, __iscsi_unbind_session);
INIT_WORK(>scan_work, iscsi_scan_session);
spin_lock_init(>lock);
+   mutex_init(>mutex);

/* this is released in the dev's release function */
scsi_host_get(shost);
diff --git a/include/scsi/scsi_transport_iscsi.h 
b/include/scsi/scsi_transport_iscsi.h
index 6183d20..acf9d9d 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -238,6 +238,7 @@ struct iscsi_cls_session {
struct work_struct unblock_work;
struct work_struct scan_work;
struct work_struct unbind_work;
+   struct mutex mutex;

/* recovery fields */
int recovery_tmo;
@@ -272,7 +273,6 @@ struct iscsi_cls_session {

  struct iscsi_cls_host {
atomic_t nr_scans;
-   struct mutex mutex;
struct request_queue *bsg_q;
uint32_t port_speed;
uint32_t port_state;



Reviewed-by: Mike Christie 


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